JPH0458073A - Syringe pump - Google Patents

Abstract

PURPOSE:To prevent the occurrence of pulsation even with no accumulator furnished while a seal member is less stained as well as to facilitate cleaning by forming a gas layer in a gap between the front face of a piston and fluid surface at least when the piston is retreated to the rearmost position. CONSTITUTION:A gas layer (air) A is formed in a gap between the front face of a piston and fluid surface when the piston 2 is retreated to the rearmost position. As a result, dispersion in pressing the piston 2 in the process of discharging fluid L is absorbed by the gas layer A, pulsation is thereby lessened at the time of feeding fluid, the installation of an accumulator is substantially not required. Even in the process of sucking/discharging fluid L, since there exists the gas layer A in the gap between the front face of the piston 2 and fluid surface, the piston 2 will never be directly brought into contact with fluid L, and a seal member (normally 'O' ring) 8 will never be brought into contact with fluid either, a device is thereby less stained, so that it is also cleaned with ease.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a syringe pump, more specifically, a syringe pump in which a piston is arranged in a cylinder so as to be able to reciprocate,
The present invention relates to a syringe pump in which a liquid inflow path and a liquid outflow path communicate with each other within the cylinder.

[Conventional technology]

Various types of pumps are known, one of which is a syringe pump. This is as shown in Figure 3.
A piston 2 is disposed within a cylinder 1 so as to be able to freely reciprocate, and a liquid inlet 3 and an outlet 4 communicate with each other within the cylinder 1, making it useful as a metering pump.

Further, a suction valve 5 is provided in the inflow path 3, and a discharge valve 6 is provided in the outflow path 4.
A sealing means 7 such as an O-ring is provided between the inner surface of the cylinder cylinder 1 and the outer surface of the piston 2.

In such a syringe pump, when the piston 2 is raised with the suction valve 5 open and the discharge valve 6 closed,
Since the inside of the cylinder tube 1 becomes negative pressure, the liquid to be supplied to the target region flows into the cylinder tube 1. When the predetermined amount of liquid has been suctioned, the suction valve 5 is closed,
When the piston 2 is lowered with the discharge valve 6 open, the liquid in the cylinder tube 1 is discharged and delivered to the target region. Such operations are performed intermittently.

[Problem to be solved by the invention]

However, in this type of syringe pump, there are basically fluctuations in the extrusion speed of the piston and vibrations, so
Pulsation during the dispensing process is essentially unavoidable. Therefore, as shown in FIG. 3, it is necessary to install an accumulator 7 on the liquid outlet side.

However, installing the accumulator 7 causes a rise in equipment costs and an increase in installation space, and should be avoided as much as possible.

On the other hand, liquid always enters between the outer surface of the piston 2 and the inner surface of the cylinder cylinder 1, so when dealing with a particularly viscous or highly adhesive liquid, the outer surface of the piston 2 and the O-ring 8 When liquid adheres between the piston 2 and the amount of adhesion increases, it is necessary to disassemble and clean it. During this cleaning, remove the entire outer surface of the piston 2 that comes into contact with the liquid and the O-ring 8 from its groove. It requires removal and cleaning, which takes a lot of effort.

Therefore, an object of the present invention is to prevent pulsation even without an accumulator and to make the seal less dirty and easier to clean.

[Means to solve the problem]

The above problem is solved by a syringe pump in which a piston is arranged in a cylinder so as to be able to reciprocate, and in which liquid flows in when the piston moves backward, and the liquid flows out when the piston moves forward. This can be solved by having a gas layer between the surface and the liquid surface.

[Effect]

In the syringe pump of the present invention, since there is a gas layer between the front surface of the piston and the liquid level at the retraction limit,
Since the uneven pushing of the piston during the liquid discharge process is absorbed in the gas layer, pulsation during feeding is reduced and installation of an accumulator is essentially unnecessary.

In addition, during the suction/discharge process, a gas layer is interposed between the front surface of the piston and the liquid surface, so the piston does not come into direct contact with the liquid.
There is no contact between the two and there is less dirt. However, when the piston is lowered to below the maximum liquid suction height, the sealing material comes into contact with a small amount of liquid remaining on the inner surface of the cylinder, but from the sealing material's perspective, it only scrapes off that small amount of liquid. This means that there is very little contamination of the sealing material compared to the conventional example, which was in almost constant contact with the liquid.
The disassembly and cleaning cycle becomes long (and even if cleaning is required, cleaning work becomes easier).

[Specific structure of the invention]

The present invention will be explained in more detail below with reference to specific examples shown in FIGS. 1 and 2.

In the present invention, as shown in FIG. 1, it is not practically necessary to install an accumulator.

Further, the device structure itself may be the same as the conventional example. However, especially in the present invention, at least the piston 2
At the retreat limit of , a gas layer A is secured between the front surface 2a and the liquid level l. More preferably, the gas is drawn in advance, taking into consideration the relationship between the stroke of the piston 2 and the amount of suction and discharge at one time, so that the forward limit (lower limit) of the piston 2 is equal to or higher than the maximum suction height of the liquid. The amount of inclusion is set.

The gas used is not limited, but air is sufficient.

A cap IA having a suction hole and a discharge hole is removably provided on the bottom surface of the cylinder cylinder I, making it convenient for cleaning, and gas can be sealed by removing the cap IA. . IB is an outer cylinder and can be used as a holder.

In the syringe pump configured in this way, when the piston 2 is raised with the suction valve 5 open and the discharge valve 6 closed, the inside of the cylinder cylinder 1 is basically the same as the conventional example. Since the pressure is negative, the liquid to be supplied to the target area flows into the cylinder cylinder 1 via the suction path 3. When the suction of a predetermined amount of liquid is completed, the suction valve 5 is closed and the piston 2 is lowered with the discharge valve 6 open and the sealed gas layer A is compressed.
Due to the compression force, the liquid in the cylinder tube 1 is gradually discharged and delivered to the target area. In this case, mechanical fluctuations (unevenness in pushing) during the downward movement of the piston 2 appear as pulsations in the supplied liquid, but since compressible air A is present, the unevenness in pushing is absorbed by air A, resulting in pulsation. is prevented.

In this discharge process, the O-ring 8 is in contact only with the gas layer A, and basically does not come into contact with gLL until the lower limit. Therefore, the cycle at the time when cleaning is required is significantly extended, and the cleaning work is relieved from the hassle.

On the other hand, if the piston 2 is lowered to below the maximum suction liquid level height of - times, the liquid sucked in the previous suction process remains on the inner surface of the cylinder cylinder 1, and in the lowering process, this small amount Although the O-ring 8 comes into contact with a large amount of liquid, it is easily rubbed off by the O-ring 8, and when the piston 2 rises again, almost no liquid adheres to the outer peripheral surface of the piston 2 and the O-ring 8. As a result, they are always kept clean, so even in this latter example, the cleaning performance is significantly improved when compared with the conventional example.

In the above example, the inflow channel 3 and the outflow channel 4 are installed separately, but in the present invention, these are connected to one pipe line through a three-way valve, etc. It can also be communicated with the cylinder tube 1.

〔Example〕

Examples will be shown below to clarify the effects of the present invention.

When feeding a photosensitive material emulsion with a viscosity of 20 cps using a syringe pump having a syringe barrel with an inner diameter of 50 mm as shown in FIGS. 1 and 2, the maximum suction height Hl of the liquid is set to 100 M. Distance H2 between limit and lower limit
When the pulsation was examined by changing the amount of air (in other words, changing the amount of air enclosed), the results shown in FIG. 4 were obtained. According to this result, it can be seen that as the amount of enclosed air increases, the pulsation decreases.

On the other hand, in the case of the conventional example without an air layer, even if an accumulator was installed, the pulsation was about 5%, indicating that the pulsation prevention effect was extremely large.

On the other hand, the necessity of cleaning was investigated while repeating liquid feeding many times.

As a result, it was found that by providing an air layer according to the present invention, the cleaning performance was improved.

In addition, when the maximum amount of liquid is being sucked, if the lower limit of the piston is higher than the liquid level, there will be no contact between the O-ring and the liquid, making cleaning easier than when it is lower. It was also found that there was a significant increase in

Further, when coating a support using the photosensitive material emulsion and examining the variation in coating film thickness, the variation was about 5% in the conventional example, whereas it was 0.
It was reduced to 6%.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent pulsation even without an accumulator, and there are advantages such as less dirt on the seal and easier cleaning.

[Brief explanation of drawings]

Fig. 1 is a front half-sectional view of a syringe pump example of the present invention, Fig. 2 is a bottom view, Fig. 3 is a front half-sectional view of a conventional example, and Fig. 4 is a correlation graph between the amount of enclosed air and pulsation. .

Claims (1)

[Claims] (1) A syringe pump in which a piston is disposed in a cylinder so as to be able to reciprocate, and in which liquid flows in when the piston moves backward, and the liquid flows out when the piston moves forward; A syringe pump characterized by having a gas layer between it and a liquid surface.